Networking

This document explains how to configure your network settings by explaining the network configuration functionality available in Funtoo Linux. Also covered is dhcpcd 5.x, Wi-Fi (IEEE 802.11) configuration, and the OpenResolv framework.

Introduction

Funtoo Linux has its own core network configuration system that differs somewhat from upstream network configuration systems used in Gentoo Linux and OpenRC.

In this document, I will explain the unique additions and changes to the Funtoo network configuration and show you how to use this system to configure your network.

I'll also explain how to use dhcpcd for managing network interfaces on DHCP-based networks, and will also cover OpenRC stacked runlevel configuration, Wi-Fi (IEEE 802.11) configuration, and the OpenResolv framework, which is enabled in Funtoo Linux by default.

A Gentle Introduction to Funtoo Network Configuration

Before I get into the technical details of configuring your network, it's important to understand that Funtoo Linux has a number of different options available to you for network configuration, with more likely to be added in the future. Each approach is different and has its own strengths and weaknesses, and this is, in my opinion, a good thing.

The Easy (Dynamic) Way

When configuring your network, one option is to skip traditional network configuration and simply rely on DHCP. This is by far the simplest method of configuring your network. If you are on a wired network, no other steps are typically required beyond enabling a DHCP client, and Funtoo Linux includes dhcpcd 7.x by default.

Network Manager, Wicd

If you are going to use a third party package such as Network Manager or Wicd to manage your network then you do not need to configure DHCP at all. These packages configure DHCP for you. Simply emerge the package you want to use and start using it.

DHCP-Only Systems

If you are not planning to use a third-party package to manage your network interfaces, it is still extremely easy to set up DHCP networking, especially if you always use DHCP to connect to networks, which is common for desktops or laptops. In this scenario, we can simply enable dhcpcd to run at system startup. It will run in the background and automatically look for DHCP servers on all your network interfaces, and will attempt to lease an IP address from any DHCP servers found.

If this sounds like what you want to do, then add dhcpcd to your default runlevel as follows:

# rc-update add dhcpcd default

To enable DHCP immediately, you would follow the previous command with an openrc command, which would start the dhcpcd client you just added:

# openrc

If you're on a wired network and have the necessary drivers in your kernel, then this should get you going. For wireless networks, more steps are required to utilize your wireless hardware to associate with an access point, which will be covered later in this document.

Tweaking Dhcpcd

For now, it's important to note that dhcpcd 7.x will manage all available network interfaces by default. If you want to run a DHCP client on all but one interface, or some other subset of interfaces, you can add the appropriate denyinterfaces or allowinterfacesglob pattern to /etc/dhcpcd.conf:

/etc/dhcpcd.conf (bash source code)

# manage all interfaces but eth0 with dhcpcd
denyinterfaces eth0

This can also be accomplished by modifying tc/init.d/dhcpcd directly and adding -Z ifglob or -z ifglob (the equivalent command-line parameters) to command_args.

Using Funtoo Scripts for DHCP

You can also use the Funtoo Linux networking scripts to start a DHCP client just on a specific interface. This approach is best if you are planning to also do some advanced bridging, bonding or VLAN configuration on your machine along with DHCP, since you will be using the Funtoo Linux networking scripts for that too.

To use this variant approach, don't enable /etc/init.d/dhcpcd directly. Instead, use the Funtoo Linux dhcpcd template which will start dhcpcd on only one interface. Below, you will see the steps to do this. This is very similar to how we set up advanced network interfaces, which will be covered later in this documentation:

Server Network Configuration

For servers and advanced networking scenarios, Funtoo Linux offers its own modular, template-based network configuration system. This system offers a lot of flexibility for configuring network interfaces, essentially serving as a "network interface construction kit." This system can be used by itself, or even combined with dhcpcd, as shown in the previous section.

Here are the key components of the template-based network configuration system:

/etc/init.d/loopback

An init script that configures the localhost interface. This script is always enabled and is part of the boot process.

/etc/netif.d

This is a directory that contains various network configuration templates. Each of these templates is focused on configuring a particular type of network interface, such as a general static IP-based interface, a bridge interface, a bond interface, etc.

/etc/init.d/netif.tmpl

This is the master init script for the template-based network configuration system. New interfaces are added to your system by creating symbolic links to this file in /etc/init.d.

So, if you wanted to use this system to configure eth0 with a static IP address, you would create a net.eth0 symlink to netif.tmpl as follows:

# cd /etc/init.d
# ln -s netif.tmpl net.eth0

Then, you would create an /etc/conf.d/net.eth0 configuration file that would specify which template to use from the /etc/netif.d directory:

When configuring your own static network interface, one of ipaddr or ipaddrs is required and should specify the IP address(es) to configure for this interface, in "a.b.c.d/netmask" format. Optional parameters include gateway, which defines a default gateway for your entire network, and if set should specify the gateway's IP address. In addition, domain and nameservers (space-separated if more than one) can be used to specify DNS information for this interface.

Configuration Variables

Interface Variables

The ipaddr and ipaddrs variables are supported by the interface and bridge templates, and are used to specify a single or multiple IPv4 or IPv6 address(es) for the interface. IP addresses should be specified in 'IP/netmask' format, such as 10.0.0.1/24. Multiple IP addresses can be specified delimited by whitespace:

ipaddrs="10.0.0.1/24 10.0.0.2/24"

Broadcast Address

By default, a broadcast address will be calculated based on the IP address and network mask. If you need to manually specify a broadcast address, use the following format for your IP address:

ipaddrs="10.0.0.1/24;broadcast=10.0.1.255 10.0.0.2/24"

Not Specifying An Address

Note that in some cases, you may choose to not specify ipaddr or ipaddrs for a bridge template. That is allowed. If you don't want to specify an IP address for a regular interface, you can choose to use the interface template without an IP address specified in the config, or use the interface-noip template instead, for the sake of clarity.

Viewing All Configured IP Addresses

Also note that if you specify multiple IPv4 addresses, ifconfig will only show the first IP address. To view all IP addresses associated with the interface, use the ip addr show command.

General Variables

The following variables are enabled by default for all network scripts, and if specified will trigger a corresponding configuration action:

nameservers

Set DNS nameservers using OpenResolv. Specify multiple IPv4 or IPv6 nameservers like this: "1.2.3.4 1.2.3.5 1.2.3.6". Please note that OpenResolv treats 127.0.0.1 specially, and it indicates that you are running a local name resolver like dnsmasq or bind. OpenResolv will ignore all other name servers specified alongside 127.0.0.1. See man resolvconf and man resolvconf.conf for additional setup information.

search

Set DNS search information using OpenResolv.

domain

Set DNS domain using OpenResolv.

gateway

Define a default IPv4 gateway on this interface.

gateway6

Define a default IPv6 gateway on this interface.

route

Specify a semi-colon delimited list of IPv4 routes to apply when this interface is brought up. Will be appended to ip -4 route add.

route6

Specify a semi-colon delimited list of IPv6 routes to apply when this interface is brought up. Will be appended to ip -6 route add.

VLAN Variables

VLAN support is enabled by default for all network configuration scripts. If a network script has a name in the format net.ethX.Y, then it is assumed to be a VLAN interface referencing trunk ethX and VLAN ID Y. If you desire a custom name for your VLAN interface, you can name your interface whatever you'd like and specify the following variables in your interface config:

trunk

VLAN trunk interface, e.g. "net.eth0"

vlan

VLAN id, e.g. "32"

Bridge / Tap Variables

The following variables for configuring a functional bridge interface with optional tap interfaces:

slaves

Set slave interfaces of this interface (for bridges, etc.) All slaves will automatically be depended upon, and will also automatically have their mtu set to that of the current interface, if an mtu is specified for the current interface. This setting is required for the bond template and optional for the bridge template.

stp

Enables Spanning Tree Protocol on a bridge interface like this "stp=on"

forwarding

Enables forwarding on a bridge interface by calling sysctl; as this interface does not exist when sysctl is called by init, we do it here. If this is disabled, your bridge will not forward traffic back out onto the network. useage: "forwarding=1"

OpenResolv and resolv.conf

OpenResolv will be used to set DNS information provided by the nameservers, domain and search variables when an interface is brought up. The OpenResolv framework will add entries to /etc/resolv.conf, and will also handle removing these entries when the interface is brought down. This way, /etc/resolv.conf should always contain current information and should not need to be manually edited by the system administrator. dhcpcd will use OpenResolv for updating system DNS information as well.

Multiple Network Configurations

For information on how to have multiple, independent network configurations, please see Stacked Runlevels.

Alternate Configs

If you need to run the same service with different configuration parameters depending upon runlevel, then you'll be happy to know that you can specify runlevel-specific conf.d files by appending a .
<runlevel> suffix. In this particular example, we could imagine a situation where we had two child runlevels named home and work:

/etc/conf.d/net.eth0.home
/etc/conf.d/net.eth0.work

Note that this feature works for all init scripts, not just network configuration scripts.

Interface Renaming

Funtoo network scripts now support interface renaming, so you can create an interface called lan if you would like. To do this, simply specify the MAC address of the interface you would like to rename using the macaddr variable:

macaddr="00:15:17:19:b6:a3"

If this MAC address is part of the net.lan configuration file, then when this interface starts, whatever interface currently has the MAC address of 00:15:17:19:b6:a3 (i.e. eth5) will be renamed to lan prior to the interface being brought up, and will show up in ifconfig and ip commands as being an interface named lan. It is possible to combine this with the mac_replace variable to set a new MAC address, if desired.

Basic VLAN Configuration

The standard interface template supports VLANs. To use VLAN support, first ensure that your kernel was compiled with VLAN support (the module name is 8021q) :

The Funtoo network configuration scripts will automatically recognize the filename net.eth1.32 as being VLAN 32 of trunk interface net.eth1.

When the VLAN interface is brought up, it will be named eth1.32.

Custom VLAN Names

However, sometimes you may want to turn off automatic file-based VLAN naming and give your VLAN interface a custom name, such as mgmt. To do this, you would set up the trunk interface in the exact same way as described above, but instead of creating a net.eth1.32 interface, you would create a net.mgmt interface, and specify vlan and trunk in the /etc/conf.d/net.mgmt config file, as follows:

Bonding Configuration

Bonding allows you to aggregate multiple network interfaces into a single logical network interface, allowing for benefits in throughput as well as resiliency in the case that an individual interface may go down. This example shows how you would create a bonding interface (mybond) with a simple static ip setup, containing two slave devices (eth0 and eth1).

First, ensure that your kernel is configured to support bonding (the module name is bonding) :

$ grep CONFIG_BONDING /usr/src/linux/.config
CONFIG_BONDING=m

You'l want to ensure that CONFIG_BONDING is set to "m" or "y". You can find this kernel configuration option tucked under "Device Drivers" -> "Network Device Support" -> "Bonding driver support".
Be sure that ifenslave is emerged (this package included in Funtoo stage3):

# emerge ifenslave

Once bonding is enabled in the kernel, you will need to choose at least two devices to bond together. These will be set up as "slave" interfaces with no IP address.

Then, configure the slave interfaces by creating /etc/conf.d/net.eth0 and /etc/conf.d/net.eth1 with the following contents:

template="interface-noip"

Now, we will create the bond interface and make net.eth0 and net.eth1 slaves of this interface. Note that our bond interface can have any name. To demonstrate this, we will give it the name of "mybond" below:

# ln -s netif.tmpl net.mybond
# rc-update add net.mybond default

Now we can configure "mybond" using its configuration file /etc/conf.d/net.mybond, just as we would a regular interface, except that we specify slaves:

In a bonded configuration, it is common to set the MTU to the maximum possible value supported by hardware to maximize throughput. In order to do this, simply set the MTU option in /etc/conf.d/net.mybond to the maximum value supported by your hardware. The network scripts will ensure that this MTU setting is applied to all slave interfaces:

mtu=9000

Bridge Configuration

When hosting virtual machines, it can be convenient to use a bridge setup. This example shows how you would create a bridge (br0) with a simple static ip setup, containing two slave devices (eth0, tap0).

First, ensure that your kernel is configured to support bridging (the module name is bridge) :

More Complex Network Configuration

If the standard templates don't work for your needs, simply create a new template -- I recommend starting from the interface template for most things:

# cd /etc/netif.d
# cp interface custom

You can now call whatever commands you need to /etc/netif.d/custom. The following shell functions can be defined in a network script:

netif_create

In netif_create, you should call any commands to create the interface if it does not yet exist.

netif_depend

In netif_depend, you can define dependencies, using the functions need and use.

netif_pre_up

In netif_pre_up, you can define network configuration actions to perform prior to bringing the interface up. You can also ensure certain variables are specified by calling require var1 [var2...] here.

netif_post_up

In netif_post_up, you can define network configuration actions to perform after bringing the interface up.

netif_pre_down

In netif_pre_down, you can define network configuration actions to perform prior to bringing the interface down.

netif_post_down

In netif_post_down, you can define network configuration actions to perform after bringing the interface down.

netif_destroy

In netif_destroy, you can call any commands necessary to destroy/delete the interface if it is dynamic in nature (tun/tap, etc.)

How It Works

You do not specify a function for actually bringing up the interface, because the template-based system does this for you. The template-based system also performs all normal actions required to bring an interface down, so you only need to specify atypical actions that must be performed - such as removing child interfaces or destroying a bridge using brctl.

When you create your own network configuration template, the following capabilities are available for use automatically, as long as the appropriate variables are set in the /etc/conf.d/netif.<ifname> file, without requiring any explicit steps on your part:

DNS configuration using domain and nameservers config settings. OpenResolv is used automatically.

License

Copyright 2009-2011 Funtoo Technologies. You can redistribute and/or modify it under the terms of the 2-clause BSD license. Alternatively you may (at your option) use any other license that has been publicly approved for use with this program by Funtoo Technologies (or its successors, if any.)